In the five positions where the indicative imperfect has final ḍamma, lam replaces it with sukūn.
Word / formMeaning / explanation
يَفْعَلُ ← لَمْ يَفْعَلْhe did not do.
تَفْعَلُ ← لَمْ تَفْعَلْyou (masc.) did not do, or she did not do.
أَفْعَلُ ← لَمْ أَفْعَلْI did not do.
نَفْعَلُ ← لَمْ نَفْعَلْwe did not do.
The same positions take fatḥa after lan but sukūn after lam: the essential difference between subjunctive and jussive here.
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Negating the Imperfect with Lan and Lam: Subjunctive, Jussive and Full Paradigms
In the five positions where the indicative imperfect has final ḍamma, lam replaces it with sukūn.
Word / formMeaning / explanation
يَفْعَلُ ← لَمْ يَفْعَلْhe did not do.
تَفْعَلُ ← لَمْ تَفْعَلْyou (masc.) did not do, or she did not do.
أَفْعَلُ ← لَمْ أَفْعَلْI did not do.
نَفْعَلُ ← لَمْ نَفْعَلْwe did not do.
The same positions take fatḥa after lan but sukūn after lam: the essential difference between subjunctive and jussive here.